Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]

[David Howells <dhowells@redhat.com>]

Stephen Smalley <sds@tycho.nsa.gov> wrote:

> They would correspond with the operations provided by the /dev/cachefiles
> interface, at the granularity you want to support distinctions to be made.

Can this be made simpler by the fact that /dev/cachefiles has its own unique
label (cachefiles_dev_t).

> Could just be a single 'setcontext' permission if that is all you want to
> control distinctly, or could be a permission per operation.

There is only one operation that makes sense to have a permission: "set
context and begin caching".

All the other operations on a file descriptor attached to /dev/cachfiles are
necessary for there to be a managed cache at all, and given that you've
managed to open /dev/cachefiles that's sufficient access for those, I think.

> If the latter, you don't really need a label for the object, and can
> just use the supplied context/secid as the object of the permission
> check, ala:
> 	rc = avc_has_perm(tsec->sid, secid, SECCLASS_CACHEFILES,
> CACHEFILES__SETCONTEXT);

Ummm.   I was under the impression that the target SID had to be a member of
target class.

David
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